Generally, in a roof panel of a vehicle, as illustrated in FIG. 1, a headlining (L) is installed at an indoor side thereof to provide a buffer function, mood or the like, as illustrated in FIG. 2. The headlining (L) is fixed to a side roof rail by a clip, and formed of various materials such as vinyl and cotton, and serves as an insulating material against a temperature change from an outside. The headlining (L) is manufactured by various methods and of various materials, as described in the following patent documents 1 to 3.
The patent document 1 discloses a manufacturing method of the headlining, which is capable of strengthening an adhesive force of each layer of an acoustic head lining, while simplifying a manufacturing process thereof, and improving reliability of a product, and also preventing a thermal deformation of polyurethane foam, and thus providing excellent acoustic absorption performance.
The patent document 2 discloses a material of a headlining for a vehicle, which includes a first layer including natural fiber, polypropylene and polyethylene terephthalate, a second layer including thermoplastic (TF) foam, and a third layer including the natural fiber, the polypropylene and the polyethylene terephthalate, and is capable of realizing high acoustic absorption performance, environment friendliness and a light weight, and a manufacturing method thereof.
The patent document 3 discloses a manufacturing method of the headlining, which is capable of providing an excellent adhesive force by using adhesive powder having a graft polymer property, being manufactured in a simple process without using an adhesive film, compared with a conventional manufacturing method using the adhesive film and adhesive powder, reducing a manufacturing cost, improving inconvenience in using the adhesive film, and also providing an acoustic absorption effect in the vehicle by forming a permeable adhesive layer. However, the conventional headlining has the following problems:
(1) In the middle of summer, when the vehicle is parked at a shadeless place for a long period of time, an internal temperature of the vehicle is increased. Therefore, to prevent the internal temperature from being increased, a window of the vehicle may be slightly opened, but in this case, it is apprehended that the vehicle or an article therein may be stolen.
(2) Such an increase in the internal temperature is caused by heat transfer through glass (door glass, front glass and rear glass) and a roof panel. To solve this problem, the glass is tinted or coated with a light protection film, and thus the increase in the internal temperature is prevented.
(3) However, since the heat is transferred through not only the glass but also the roof panel which occupies most of a ceiling of the vehicle, a high-priced heat shielding material may be used to prevent the heat transfer. This causes a high manufacturing cost and also causes the fuel efficiency of the vehicle to be lowered.
(4) Meanwhile, when the internal temperature of the vehicle is increased, a child or the old and the infirm may suffer from heat exhaustion or heatstroke, and a lighter or a canned drink may be exploded by thermal expansion and thus may contaminate the vehicle or may cause a fire.
(5) Therefore, in the case of the roof panel exposed to direct sunlight during the summertime, a temperature thereof is very high, and thus it is necessary to prevent the heat from being transferred to the inside of the vehicle through the roof panel, and thus to prevent a safety accident.